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Tuesday, January 26, 2016

Into the Den of the Devil Dog

By Jim Godwin and Lesley de Souza

Part I.

The time was mid-afternoon 15 September 2015 and wewere in our first full day of intensive Eastern Hellbender surveys that were to continue over the next two weeks. We began this day on Big Nance Creek in Lawrence County, Alabama. This stream was selected because it’s within the range of the Eastern Hellbender, had never been searched, and had accessible stream-road crossings for canoe drop-off and take-out. What we did not anticipate was what lay between those points.

On the stream this day were Sara Piccolomini and Tom Floyd in one of the Dagger Legend canoes while we were in the other. The day, in early fall, was one of clear skies and warm temperatures (hey, this is Alabama after all). Soon after beginning the float we encountered stream stretches with nice appearing habitat, stream channels with water flowing over flat rocks and a gravel and cobble substrate. Tom donned a mask and snorkel and dove under to turn rocks. While the general appearance of the habitat was promising the stirring of silt from the lifting of rocks was a cause for concern. Accumulations of silt and sediment are indicators of degraded water quality, the general underlying cause for the decline of the hellbender and other aquatic species in Alabama.

As we progressed downstream we began to encounter a few trees lying in and across the channel, but downed trees in stream channels are part of the ecological life of the stream. Big Nance Creek is on the south side of the Tennessee River and flows north to the river. As we floated down the stream we searched for Hellbenders at promising locations and collected water samples for an analysis for Hellbender DNA, a method commonly known as environmental DNA (eDNA). At each eDNA sampling point the weight in our canoe increased and once we had filled all our bottles we were carrying an extra 68 lbs. more than when we had started out that morning. Later in the day we would feel the weight of every pound of water….

The Eastern Hellbender (Cryptobranchus alleganiensis; aka snot otter, lasagna lizard, devil dog, grampus, and a few others colloquial names) is one of the largest salamanders in North America and may attain a total length approaching ¾ of a meter. Its range spans New York to Alabama. In Alabama this fully-aquatic salamander, with fleshy folds running the length of the body between the limbs, is found only in the very northern counties where it occupies streams draining into the Tennessee River. Although we lack historical information on population sizes, overall hellbender numbers appear to have declined and we attribute this to degradation of water quality from sedimentation, siltation, channelization, and impounding of streams. Museum records dating back into the 1960s and 70s document localities in numerous streams of northern Alabama counties, yet the current status of the species is unknown. To remedy this lack of information we are performing surveys this year and next through studies funded by the Alabama Department of Conservation and Natural Resources.

Why is excess sedimentation and siltation an issue for the hellbender? Good habitat for the Hellbender are streams with cool, clear, well oxygenated water that have a substrate with an abundance of large flat rocks overlying a layer of gravel and cobble. Since hellbenders respire cutaneously their skin presents a large surface area for gas exchange between the hellbender and the water. Elevated loads of suspended solids in the water will hamper the Hellbender’s ability to take up dissolved oxygen from the water. Hellbenders occupy cavities beneath flat rocks in the streams; their flattened bodies allow them to squeeze into the tight spots but they also shape cavities by shifting around gravel. During the breeding season a male’s cavity may become a brood chamber for eggs. Following oviposition by the female a male will guard and, using his lateral folds of skin, circulate water over the eggs. Abnormally high levels of sedimentation reduces dissolved oxygen content in water and sifts down and fills spaces in the gravel and cobble, and invades and chokes out cavities under rocks. The end result of this is a loss of hellbender habitat for the brooding of eggs and day-to-day refugia for adult and juvenile animals. These degradative effects have ramifications throughout the aquatic system, including everything from insects, crayfish, bivalves, snails, fish and other species.

The typical method in searching for Eastern Hellbenders is to wade or snorkel in shallow streams and lift large flat rocks. Hellbenders take refuge under rocks as do many other aquatic species. Over the years the visual surveys and hand captures have been the means by which most Hellbenders have been collected, although occasionally one will be hooked by a fisherman or taken on a trotline. In recent years a new technique integrating field and lab methods has emerged, a technique informally termed environmental DNA (eDNA). The Hellbender, and other aquatic species, shed cells and tissue which is carried along in the water column. This cellular material has been termed environmental DNA and can be collected and analyzed. The collections and subsequent analysis of a water sample can reveal the presence of Hellbender DNA from streams containing the species. The field method is straight-forward, with a decontaminated one liter bottle a sample of stream water is collected and passed through a filter thus isolating the cells and tissues from the water sample. From this stage the filters go to the lab where the DNA is chemically extracted. DNA extracts are then screened for Hellbender DNA with a primer specific to the species.

Biologists throughout the range of the Eastern Hellbender are concerned about the conservation of the species and researchers are incorporating both standard sampling and eDNA techniques to assess the status of the species. In Alabama we also are utilizing both methods and since eDNA has been shown to be more sensitive to detecting the presence of the hellbender we expect to locate streams previously unknown to contain hellbenders, if they are present.

The late summer and fall in Alabama are normally times oflow water levels in the streams which may not be good for a recreational float but produce optimum conditions for searching for aquatic life and collecting water samples. But the low water conditions often present other challenges. We had expected that we would encounter very shallow riffles and need to drag canoes through these low water spots, what we did not anticipate were the log jams. Somewhere north of AL highway 157 on Big Nance Creek the occurrence of downed trees rose dramatically, as did our observations of cottonmouths.

We began to encounter channel-choking logjams one after the other and with a good five or six miles remaining before reaching the take-out. We were able to negotiate many of the logjams by lifting the front of the canoe upon a low tree trunk and dragging it over with short orchestrated bursts of pulling. “On the count of three, pull!” Remember the 68 lbs. of water samples? Those were in a plastic box at the center of the canoe and always required a little extra oomph to pull across the log. As we made our way downstream we encountered deeper waters that would require a parallel realignment of the canoe so that we could step out onto the log. After that a perpendicular alignment of the canoe for pulling it over the log while we did balancing acts to avoid a good dunking.

We were hitting these passage-blocking logjams every 100 to 200 yards count of the number of logjams that had been negotiated. As the sun began to drop lower we were faced with decisions. Our parties had become separated. We were much further down the stream than Sara and Tom. Where were they and had they encountered other difficulties? We called and texted Sara but as we later learned the battery in her phone was running very low. Tom’s phones were safely ensconced in a dry bag in our canoe. At one stop where we had a good view downstream we waited about 15 minutes for Sara and Tom; they never appeared. Because we were rapidly losing daylight we decided to push on and try to reach the take-out.

We met the final logjam of the day. Large trees were completely blocking the channel and in the dimming light we could see only two possible routes. To take the “easier” route we would have to push through an accumulation of duckweed and floating debris. We gave it a try but could not force the canoe through the trash. A second route was possible along the left bank. This would necessitate a portage of gear and a dragging of the empty boat up along the bank past the trunk of the tree. Our third option was to secure the canoe, grab the important items, and walk out. By this time darkness had fallen and so we walked out. We were within a mile or so of the take-out. We walked out across a large hay field to a county road which led to the road where the truck was parked. It was a nice night for a walk under clear skies and a sliver of the moon. But where were Sara and Tom? We had connected by text and knew they were safe and had made the same decision to leave their canoe on the water, but we know not exactly where they were.

Lesley de Souza received her Ph.D. from Auburn University focused on Neotropical fishes, since then her work has centered on Arapaima research and conservation in Guyana. On-going studies on eDNA and conservation of the Black Warrior Waterdog, Flattened Musk Turtle, and Eastern Hellbender have kept her aquatically connected to the southeastern United States. Check out her website.